1. Field of Invention
The invention relates to a fan and, in particular, to a fan having a heat dissipating structure.
2. Related Art
In a general structure of a fan, the impeller is coupled to the motor and driven by the motor to rotate so as to supply sufficient airflow volume to the heat generating device or space for the purpose of heat dissipation. So, the current fan designers and manufacturers make efforts in the kind of fan that can provide more airflow. One way to increase the airflow of the fan is to raise the rotation speed of the fan. However, when the fan rotates at a high speed, the blades of the fan will bear extremely high pressure and may be thus deformed and even broken, resulting in a very dangerous situation. Thus, the rotation speed can not be raised unlimitedly in the design of the fan.
Besides, at the high-speed rotation, the motor's structure and bearings will be subjected to a large burden, which heavily threatens the lifespan of the product. Moreover, because the motor is disposed within the impeller, the heat generated by the motor can not be smoothly dissipated due to the impediment of the impeller. In this situation, the bearings of the motor will be easily damaged and the lifespan of the motor is thus reduced. Besides, the temperature within the system will increase accordingly and the lifespan of the fan is thus reduced.
Furthermore, some fans that can generate high airflow pressure, such as centrifugal fans, are commonly applied to a heat dissipating apparatus of a complex system, such as a communication cabinet or a frequency converter cabinet, and these heat dissipating apparatuses will generate an environment up to 70° C. The temperature of the motor operating in the 70° C. environment will reach 100° C., which will reduce the lifespan of the motor's bearing a lot.